The physical allergies comprise a heterogeneous group of disorders in which signs and symptoms of the immediate-type hypersensitivity reaction are precipitated by physical stimuli such as exercise, cold, and pressure. The mast cell appears central to the pathophysiology of the physical allergies. Thus, the physical allergies afford a unique opportunity to study the contribution of the mast cell inflammatory responses. To achieve these goals, we plan to biopsy patients with specific physical allergies. Within the biopsied tissues we will study mast cells, carefully characterizing their ultrastructural patterns of activation-secretion and recovery, their phenotypes (as defined by ultrastructural and immunocytochemical criteria), and their density, distribution, and state of activation. Furthermore, we will evaluate endothelial cells for evidence of activation, a possible consequence of released cytokines from mast cells. Skin samples will be studied after biopsy at specified times before, during, and after physical stimulus-specific elicitation of urtication. Controls will include identical studies of mast cells in normal tissues and dermatitides that mimic the physical allergies. Findings will be quantitated and apparent differences tested for statistical significance.